The proposed investigation is concerned with the mechanism of antigen- induced inhibition of experimental allergic encephalomyelitis (EAE). Two types of studies are planned: 1) We shall attempt to indentify the peptide determinant(s) of the myelin basic protein (BP) molecule which is responsible for induction of unresponsiveness to EAE. Subsequently we will study the relationship of this site to the disease-inducing determinant at the molecular and cellular level. 2) We shall determine whether antigen-induced unresponsiveness to EAE is due to blocking antibody or a true state of tolerance at the level of the lymphocyte.